Connecting 5v on 3.3v device. Holly smooooooke.

What kinda fucked up 3.3 doesnt have a 5->3.3 stepdown??

@sharktits raspi gpio 😂
While it doesn't seem to fuck up your entire board anymore, stuff like spi etc. still won't work on 5v

@electric-ghost try some esp-01 modules. Esp-01 work on 3.3v. Not 5v. Now, I know :p

@Kimmax i never burned a Raspi. But some ATmega328 and others stuff burn like a charm 🤭🤫

I use 3.3v on every circuit as logic high. It will save your hardware and make it compatible with most of components in the market.
You can down from 5v to 3.3v with a voltage divider (1k-2.2k). Also if you need 5v you can connect the 3.3v directly as it's enough to be a logic high.

Oh and never forget put a resistor when connecting microcontrollers. Use a low one to not reduce the bandwidth but enough to limit the current to 10mA/15mA.

@LuxARTS The resistor divider will only do the job for slow enough signals, of course. And connecting 3.3 V level signals to a 5 V device will only work reliably for TTL inputs, not CMOS.

@7400 You're right. I was thinking about microcontrollers when wrote it.

@LuxARTS thx for that. But you’re talking about rx and tx right? Not vcc? With voltage divider, the esp had not enough ma. Thx.

@mk3d Of course! The voltage divider can be used in low current situation only. For power supplies must use a regulator (LM7833 or LM317 with calculated resistors). A switching step-down can be used too to get better efficiency but it's expensive.

@LuxARTS just to be sure ;)
For vcc, I’ve tried diode (1n4004) and that’s work fine. Want try with regulator like ams1117 but need capacitors. I really like the diode approach described here: http://yaab-arduino.blogspot.com/20...

@mk3d You can down to 3.6v using 2 diodes in serial (must be Silicon ones) to get ~1.4v voltage drop from 5v but it's not recommended because if you connect 3.3v from another microcontroller to 3.6v you have a potential difference of 0.3v and doing the math: 0.3v/0 ohm(the wire) = ∞ current = short circuit. Of course you can't get infinite current and that's why the output and/or input will die.

@mk3d Btw, I didn't mention the AMS1117 cause it comes in SMT package only and sucks for testing circuits over protoboard.

@LuxARTS thx for infos! Will try with AMS1117. And stop using diodes ;)